a) Field of the Invention
The present invention relates to rock grinding mills and more particularly to rock grinding mills into which rocks to be ground and water are directed, and the grinding mill section is rotated about a longitudinal center axis to cause the rocks to travel upwardly in a curved path to tumble back to impact other rocks to cause the rock to break up into smaller fragments.
b) Background Art
For many industrial purposes it is necessary to reduce the size of rather large rocks to a much smaller particle size (commonly called “comminution”). For example, the rocks may be blasted out of an area, and these larger rocks (sometimes the size of boulders) are then directed into a grinding mill. One common form of a grinding mill is where there is a large cylindrical grinding section which often could have a diameter of as much as ten to fifty feet. The rocks along with water or air is directed into one end of the continuously rotating grinding section, and there are various types of lifting ribs positioned on the inside surface of the grinding section to carry the rocks upwardly in a curved upwardly directed path within the grinding chamber so that these tumble back onto other rocks in the lower part of the chamber. Thus, these rocks impact each other and are broken up into smaller rock fragments. Also, sometimes large iron balls (e.g., two to six inches in diameter) are placed in the grinding chamber to obtain improved results.
It takes a tremendous amount of power to operate these grinding mills, and also there are other substantial costs involved. There are a number of factors which relate to the effectiveness and the economy of the operation, and the embodiment of the present invention is directed toward improvements in such mills and the method employed.